The proposed work is based on the premise that: first, alcoholism is genetically influenced; second, studying children of alcoholics might help identify potential markers of a predisposition towards alcoholism; and third, on data demonstrating that sons of alcoholics (FHPs) show a decreased intensity of reaction to ethanol when compared to sons of nonalcoholics. Our immediate goals are to further characterize this decreased intensity of reaction to ethanol, to begin to narrow down the number of potential psychological/cognitive contributors to this phenomenon, and to hone in on possible physiological/biochemical mechanisms contributing to the decreased intensity of reaction in FHPs. We propose to begin to accomplish these tasks by using our research approach to determine the generalizability of the decreased reaction to ethanol to the level of reaction to another CNS depressant, diazepam. In this proposal, healthy, drinking and nonalcoholic sons of alcoholics age 21 to 25 will be matched with sons of nonalcoholics on demography, drinking and drug use histories, and height to weight ratio. Selected individuals will then be brought to the laboratory on 4 occasions where they will be challenged in turn with 0.7 ml/kg of ethanol plus palcebo diazepam, 0.1 mg/kg of diazepam plus palcebo ethanol, 0.2 mg/kg of diazepam plus ethanol, and placebo ethanol plus placebo diazepam and their reactions observed over the subsequent four hours. The intensity of reaction tot he challenge drug will be monitored through subjective and observer ratings of levels of intoxication, cognitive/psychomotor measures before and after the drug challenge, and hormonal responses during the laboratory session.